Presentation Speech by Professor Tord Claeson
of the Royal Swedish Academy of Sciences,
December 10, 2000.
Translation of the Swedish text.
|Professor Tord Claeson delivering the
Presentation Speech for the 2000 Nobel Prize in Physics at
the Stockholm Concert Hall.
Copyright © Nobel Media AB 2000
Photo: Hans Mehlin
Your Majesties, Your Royal Highnesses,
Ladies and Gentlemen,
Information technology (IT) influences our lives at many levels. We use it to collect, process, communicate and present information. IT controls high-tech processes as well as medical diagnostic instruments and everyday home appliances. Computers are linked in a global network and only a few years from now, they will number one billion. The performance of microelectronic circuits seems to be increasing one hundred-fold every ten years - at unchanged prices. IT is viewed as a prime mover in the economic upswing our society has experienced over the past decade.
This year's Nobel Prize in Physics rewards contributions to the early developments of microelectronics and photonics, focusing on the integrated circuit, or "chip," as well as semiconductor heterostructures for lasers and high-speed transistors.
The transistor was invented around Christmas 1947 and the discoverers of the transistor effect were awarded the 1956 Nobel Prize in Physics. Ten years after that discovery, transistors had replaced vacuum tubes on a large scale. Beaches were being flooded by pop music, and one of the inventors is said to have exclaimed: "If only I had never invented that transistor."
Discrete transistors were soldered on circuit boards together with other components. But the emerging computers required ten thousands of transistors on the same board, a time-consuming and error-prone task.
As a newly hired engineer, Jack Kilby did not get his two weeks of vacation in the summer of 1958. Instead he had the privilege of thinking undisturbed on working time. He designed a circuit out of components made from a single semiconductor material that had been processed in different ways. This had already been suggested, but it was in conflict with the prevailing industrial practice of producing parts in the cheapest available material. On September 12, he was able to demonstrate that an integrated circuit worked - the birth date of the integrated circuit is one of the most important birth dates in the history of technology. Since then, things have moved fast. Chips being made today contain nearly a billion bits of memories or logic gates in processors - the brains of computers.
What was needed was not only more, smaller and cheaper transistors, but also faster ones. Early transistors were relatively slow. Semiconductor heterojunctions were proposed as a way of increasing amplification and achieving higher frequencies and power. Such a heterostructure consists of two semiconductors whose atomic structures fit one another well, but which have different electronic properties. A carefully worked out proposal was published in 1957 by Herbert Kroemer. Today, high-speed transistors are found in mobile (cellular) phones and in their base stations, in satellite dishes and links. There they are part of devices that amplify weak signals from outer space or from a faraway mobile telephone without drowning in the noise of the receiver itself.
Semiconductor heterostructures have been at least equally important to the development of photonics - lasers, light emitting diodes, modulators and solar panels, to mention a few examples. The semiconductor laser is based upon the recombination of electrons and holes, emitting particles of light, photons. If the density of these photons becomes sufficiently high, they may begin to move in rhythm with each other and form a phase-coherent state, that is, laser light. The first semiconductor lasers had low efficiency and could only shine in short pulses.
Herbert Kroemer and Zhores Alferov suggested in 1963 that the concentration of electrons, holes and photons would become much higher if they were confined to a thin semiconductor layer between two others - a double heterojunction. Despite a lack of the most advanced equipment, Alferov and his co-workers in Leningrad (now St. Petersburg) managed to produce a laser that effectively operated continuously and that did not require troublesome cooling. This was in May 1970, a few weeks earlier than their American competitors.
Lasers and light emitting diodes (LEDs) have been further developed in many stages. Without the heterostructure laser, today we would not have had optical broadband links, CD players, laser printers, bar code readers, laser pointers and numerous scientific instruments. LEDs are used in displays of all kind, including traffic signals. Perhaps they will entirely replace light bulbs. In recent years, it has been possible to make LEDs and lasers that cover the full visible wavelength range, including blue light.
I have emphasized the technical consequences of these discoveries, since these are easier to explain than the spectacular scientific breakthroughs that they have also led to. Challenging problems and matching resources have led to large-scale basic research. The advanced materials and tools of microelectronics are being used for studies in nanoscience and of quantum effects. Scientific experiments and computations are, of course, highly computerized.
Semiconductor heterostructures can be regarded as laboratories of two-dimensional electron gases. The 1985 and 1998 Nobel Prizes in physics for quantum Hall effects were based on such confined geometries. They can be reduced further to form one-dimensional quantum channels and zero-dimensional quantum dots for future studies.
Drs. Alferov, Kilby and Kroemer,
I have briefly described some consequences of your discoveries and inventions. Few have had such a beneficial impact on mankind as yours. I also predict that there will be continued development, as we may be only halfway through the information technology revolution. New effects may appear as a result of basic research. When, what and where we cannot say, but we can be sure they will come.
On behalf of the Royal Swedish Academy of Sciences, I would like to convey the warmest congratulations to you and ask you to step forward to receive the Nobel Prize from the hands of His Majesty the King.
Copyright © The Nobel Foundation 2000